Initial Coordinates Research Articles

Non-contact measurement method of displacement of spherical joints in long-span space steel structures

For long-span space steel structures after a long period of operation, it is crucial to quickly and accurately measure the deformation for structural safety evaluation. To address the challenges in deformation measurement of space steel structures, this paper presents a non-contact, three-dimensional coordinate measurement method for key ball joints in their spatial positions. A high-precision Laser Total Station is utilized to measure the surface of the ball joints at multiple points. Three-dimensional coordinates of the center of the ball joints are then accurately determined by using three-dimensional analytical method and the least square error method. Subsequently, the deformation of key joints of the long-span space structures is obtained by comparing the determined coordinates with their initial coordinates. An engineering application by adopting the propose method to measure the deformation of a large-span steel structure gymnasium in Guangdong Province is presented. This method not only can be used to evaluate the safety of existing space steel structures, but also can be applied to rapid measurements and positioning of new long-span steel structures to improve the measurement efficiency and personnel safety.

Numerical search for time-of-flight focusing conditions and its application to the analysis of TOF mass analyzer schemes

A method of searching for high-order time-of-flight focusing conditions based on data of numerical trajectory analysis of corpuscular-optical systems is presented. The method makes it possible to determine the maximum achievable order of focusing, the value of the independent variable (initial coordinate, initial angle, initial velocity or energy) relative to which the focusing is observed, as well as the spatial position of focus. The method has been tested on model problems. The corpuscular-optical properties of time-of-flight devices with known analytical solutions are investigated, and the uniqueness of their parameters in their class is shown.

Statistical analysis of coupled oscillations with a single fixed endpoint and its application to carbon nanomaterials

Squared deviations from the equilibrium positions of one-dimensional coupled harmonic oscillators with fixed and free endpoints are calculated, and the time averages are expressed as a function of the initial displacements and velocities. Furthermore, we consider the averages of squared deviations over an ensemble of initial displacements and velocities, which distribute based on a product of the same distribution functions with variances of the initial coordinates σx2 and velocities σv2 , respectively. We demonstrate that the mean squared deviation linearly increases as the oscillator separates further from the fixed endpoint because of the asymmetrical boundary conditions, and that the increase rate depends only on σv2 and not on σx2 . This simple statistical property of harmonic oscillation is similarly observed in the oscillations of a graphene sheet and carbon nanotube in molecular dynamics simulations, in which the interacting forces are nonlinear.

Tracking conformational transitions of the gonadotropin hormone receptors in a bilayer of (SDPC) poly-unsaturated lipids from all-atom molecular dynamics simulations.

Glycoprotein hormone receptors [thyrotropin (TSHR), luteinizing hormone/chorionic gonadotropin (LHCGR), and follicle stimulating hormone (FSHR) receptors] are rhodopsin-like G protein-coupled receptors. These receptors display common structural features including a prominent extracellular domain with leucine-rich repeats (LRR) stabilized by β-sheets and a long and flexible loop known as the hinge region (HR), and a transmembrane (TM) domain with seven α-helices interconnected by intra- and extracellular loops. Binding of the ligand to the LRR resembles a hand coupling transversally to the α- and β-subunits of the hormone, with the thumb being the HR. The structure of the FSH-FSHR complex suggests an activation mechanism in which Y335 at the HR binds into a pocket between the α- and β-chains of the hormone, leading to an adjustment of the extracellular loops. In this study, we performed molecular dynamics (MD) simulations to identify the conformational changes of the FSHR and LHCGR. We set up a FSHR structure as predicted by AlphaFold (AF-P23945); for the LHCGR structure we took the cryo-electron microscopy structure for the active state (PDB:7FII) as initial coordinates. Specifically, the flexibility of the HR domain and the correlated motions of the LRR and TM domain were analyzed. From the conformational changes of the LRR, TM domain, and HR we explored the conformational landscape by means of MD trajectories in all-atom approximation, including a membrane of polyunsaturated phospholipids. The distances and procedures here defined may be useful to propose reaction coordinates to describe diverse processes, such as the active-to-inactive transition, and to identify intermediaries suited for allosteric regulation and biased binding to cellular transducers in a selective activation strategy.

Keeping track of time: Horizontal spatial biases for hours, days, and months.

In many Western cultures, the processing of temporal words related to the past and to the future is associated with left and right space, respectively - a phenomenon known as the horizontal Mental Time Line (MTL). While this mapping is apparently quite ubiquitous, its regularity and consistency across different types of temporal concepts remain to be determined. Moreover, it is unclear whether such spatial mappings are an essential and early constituent of concept activation. In the present study, we used words denoting time units at different scales (hours of the day, days of the week, months of the year) associated with either left space (e.g., 9 a.m., Monday, February) or right space (e.g., 8 p.m., Saturday, November) as cues in a line bisection task. Fifty-seven healthy adults listened to temporal words and then moved a mouse cursor to the perceived midpoint of a horizontally presented line. We measured movement trajectories, initial line intersection coordinates, and final bisection response coordinates. We found movement trajectory displacements for left- vs. right-biasing hour and day cues. Initial line intersections were biased specifically by month cues, while final bisection responses were biased specifically by hour cues. Our findings offer general support to the notion of horizontal space-time associations and suggest further investigation of the exact chronometry and strength of this association across individual time units.

Generating Mathematical Expressions for Estimation of Atomic Coordinates of Carbon Nanotubes Using Genetic Programming Symbolic Regression

The study addresses the formidable challenge of calculating atomic coordinates for carbon nanotubes (CNTs) using density functional theory (DFT), a process that can endure for days. To tackle this issue, the research leverages the Genetic Programming Symbolic Regression (GPSR) method on a publicly available dataset. The primary aim is to assess if the resulting Mathematical Equations (MEs) from GPSR can accurately estimate calculated atomic coordinates obtained through DFT. Given the numerous hyperparameters in GPSR, a Random Hyperparameter Value Search (RHVS) method is devised to pinpoint the optimal combination of hyperparameter values, maximizing estimation accuracy. Two distinct approaches are considered. The first involves applying GPSR to estimate calculated coordinates (uc, vc, wc) using all input variables (initial atomic coordinates u, v, w, and integers n, m specifying the chiral vector). The second approach applies GPSR to estimate each calculated atomic coordinate using integers n and m alongside the corresponding initial atomic coordinates. This results in the creation of six different dataset variations. The GPSR algorithm undergoes training via a 5-fold cross-validation process. The evaluation metrics include the coefficient of determination (R2), mean absolute error (MAE), root mean squared error (RMSE), and the depth and length of generated MEs. The findings from this approach demonstrate that GPSR can effectively estimate CNT atomic coordinates with high accuracy, as indicated by an impressive R2≈1.0. This study not only contributes to the advancement of accurate estimation techniques for atomic coordinates but also introduces a systematic approach for optimizing hyperparameters in GPSR, showcasing its potential for broader applications in materials science and computational chemistry.

Дослідження показників точності моделей нелінійних динамічних систем

The development and improvement of methods for calculation and control of functioning processes and operating modes of technical systems, including electronic control and modeling tools, is a serious scientific problem that has actual applied significance. Carrying out calculations to ensure the qualitative optimization of the parameters of technical means in various categories, the organization of effective production and operational control is possible only on the basis of the creation of effective methods and algorithms for the analysis of functioning processes and the accuracy of complex structures and schematic diagrams of systems and devices that are designed and developed. When developing these methods and algorithms, a set of complex scientific problems arises, the solution of which requires a number of scientific studies. The task of assessing the impact of deviations of the parameters of nonlinear dynamic systems on their movement and quality indicators is considered. Both when analyzing the accuracy of dynamic systems and when solving synthesis problems with accuracy conditions, the ability to analytically express the additional motion of dynamic systems is of great importance. The corresponding formulas for the deviations of the trajectories of the dynamic system relative to the reference trajectory and relative to the excited motion were obtained and analyzed. A method of rational determination of interpolation nodes when calculating functionals from the initial coordinates of the dynamic system is proposed. The technique refers to the selection of Gaussian quadrature nodes when calculating the quality indicators of dynamic systems with the smallest calculation error.

Citric acid and temperature programming assisted synthesized Vanadium Silicate-1 for oxidative desulfurization of dibenzothiophene

Vanadium-MFI zeolites possess phenomenal potential for catalytic oxidation, while their application is constrained by vanadium content and species distribution. Here, we constructed Vanadium Silicate-1 (VS-1) with enhanced content and preferable distribution by the addition of citric acid in tandem with a temperature-program strategy. Citric acid could modulate the pH in the initial gel and coordinate with vanadium, inhibiting the hydrolysis of vanadium and promoting vanadium incorporation. Moreover, a temperature program was employed to generate unsaturated silicon species, overcoming the tendency of aggregation in vanadium precursor and further promoting vanadium insertion. Furthermore, the effects of the first-stage crystallization temperature and time on the properties of zeolite have been investigated in detail. The sample synthesized through the optimal temperature program achieved 99.9 % dibenzothiophene conversion in 2 h, 10.4 times that of conventional synthesis. To explain the excellent reaction activity, the relationship between different vanadium species and reaction results was investigated. Through linear fitting, V=O(OSi)2(OH) was considered as the dominant active species in oxidative desulfurization (ODS) reaction. Notably, the recycled zeolite proved good reusability, further enhancing its promising application prospect.

Radial and translational motions of a gas bubble in a Gaussian standing wave field

Acoustic waves with a finite beam width are widely used in acoustic manipulation and cavitation applications. In view of this, radial oscillation and translational motion of a gas bubble in a Gaussian standing wave field are studied in this work. Dynamic differential equations for the bubble are derived with the axial and transverse motions coupled with each other. A comprehensive numerical study is also carried out in the parameter space of the driving frequency, pressure amplitude, initial coordinate, off-axial distance and beam waist. The results demonstrate that the nonlinear radial oscillation can be intensified by a higher pressure amplitude and a smaller off-axial distance. Whether the driving frequency is much lower than the resonance frequency determines not only the final equilibrium position but also the direction of translational motion for the gas bubble. With the widening of the Gaussian standing wave, the radial oscillation will be weakened and the translational motion will be slowed down due to reduction of the pressure gradient regardless of the driving frequency. The results obtained in this study is of interest for an understanding of the bubble dynamics in non-plane acoustic wave fields.

The Optimal Targeting for Focused Ultrasound Thalamotomy Differs between Dystonic and Essential Tremor: A 12-Month Prospective Pilot Study.

Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy is increasingly used to treat drug-resistant essential tremor (ET). Data on MRgFUS thalamotomy in dystonic tremor (DT) are anecdotal. To investigate efficacy, safety, and differences in target coordinates of MRgFUS thalamotomy in DT versus ET. Ten patients with DT and 35 with ET who consecutively underwent MRgFUS thalamotomy were followed for 12 months. Although in both groups the initial surgical planning coordinates corresponded to the ventralis intermediate (Vim), the final target could be modified intraoperatively based on clinical response. Tremor significantly improved in both groups. The thalamic lesion was significantly more anterior in DT than ET. Considering both ET and DT groups, the more anterior the lesion, the lower the odds ratio for adverse events. MRgFUS thalamotomy is safe and effective in DT and ET. Compared to classical Vim coordinates used for ET, more anterior targeting should be considered for DT.

IMPROVING OPERATIONAL SAFETY OF NPP STEAM GENERATORS BY CONTROLLING STEAM HUMIDITY

The article considers the possibility of increasing the safety of NPP power units operation by improving the quality of steam generator water supply control. The quality of control is improved by introducing a new information signal about steam humidity before the turbine. The necessity of introducing this signal is substantiated. The article describes the properties of the object of regulation by various channels, the initial coordinate for which is steam humidity.

Integrating AlphaFold and deep learning for atomistic interpretation of cryo-EM maps.

Interpretation of cryo-electron microscopy (cryo-EM) maps requires building and fitting 3D atomic models of biological molecules. AlphaFold-predicted models generate initial 3D coordinates; however, model inaccuracy and conformational heterogeneity often necessitate labor-intensive manual model building and fitting into cryo-EM maps. In this work, we designed a protein model-building workflow, which combines a deep-learning cryo-EM map feature enhancement tool, CryoFEM (Cryo-EM Feature Enhancement Model) and AlphaFold. A benchmark test using 36 cryo-EM maps shows that CryoFEM achieves state-of-the-art performance in optimizing the Fourier Shell Correlations between the maps and the ground truth models. Furthermore, in a subset of 17 datasets where the initial AlphaFold predictions are less accurate, the workflow significantly improves their model accuracy. Our work demonstrates that the integration of modern deep learning image enhancement and AlphaFold may lead to automated model building and fitting for the atomistic interpretation of cryo-EM maps.

Peramalan Titik Akuifer Di Desa Manistutu Kecamatan Melaya Kabupaten Jembrana Dengan Metode Geolistrik

Research has been carried out which aims to determine the depth of the aquifer point in Manistutu Village, Melaya District, Jembrana Regency. The work process of this research is the first to collect data directly using a geoelectric device with a Wenner configuration. Electric current is passed below the earth's surface through current electrodes that are installed above the earth's surface. The data that has been collected is then processed using Res2Div version 3.53g for 2D. The result of the software is a 2D image which is a direct lateral view of the subsurface structure. Of the two identified paths, namely line 1 at initial coordinates 8°31'92.33"S, 114°55'94.59"E to final coordinates 8°31'78.07"S, 114°56'05.21"E, the lowest resistivity value is obtained 121 Ohm m with a depth of 13 m and 20 – 32 m which is suspected as an aquifer point. On track 2 with initial coordinates 8°31'55.56"S, 114°56'08.31"E to final coordinates 8°31'55.56"S 114°56'61.11"E the resistivity value is 2.56 Ohm m to 8952 Ohm m. The layer that is suspected as an aquifer point is at a depth of 18.5 m, because of its low resistivity value.

Eye detection and coarse localization of pupil for video-based eye tracking systems

A video-based eye tracking system generally captures NIR images, each of which contains one or two eyes of a subject. The subject’s point of gaze is then determined using 3D eye model and pupil centre corneal reflection technique. Eye detection and pupil localization play significant roles in video-based eye tracking systems. However, face rotation, wearing glasses, eye-shape variation and illumination variation make it difficult to detect an eye and localize a pupil accurately in the images captured by video-based eye tracking systems. In this paper, we proposed an eye detector that adopts a coarse-to-fine strategy. The eye detector consists of three classifiers: an ATLBP-THACs feature-based cascade classifier, a branch CNN and a multi-task CNN. We also proposed a method for coarse pupil localization. Coarse localization is an important step for pupil localization since it can provide initial pupil coordinates for a fine pupil localization method. Given a downscaled eye image, a shallow CNN is used to estimate the location of seven landmarks. On this basis, pupil center and radius are estimated. A method for small dim target enhancement is used to increase the contrast between pupil and background. The main goal of pupil enhancement is to make it easier to binarize an eye image. At last, component filtering is made by utilizing the estimated pupil center and radius. We collected a dataset named neepuEYE dataset that consists of 5500 NIR eye images from 109 people. The images can be used to generate augmented samples for training an eye detector since they contain eyes with different shape, orientation and pupil localization. Experimental results show that our eye detector is a fast and robust detector. Furthermore, our method for coarse pupil localization can obtain not only high detection rate but also high localization speed.

Beam shaping for two-dimensional laser array by a computational model

The application of two-dimensional array laser source is more and more popular. Currently, many methods have been proposed for the collimation of laser beams; however, there is still a lack of research for the collimation of array laser sources so far. This paper presents a collimating method for array laser source. Through the calculation of the lens surfaces, the shape of the illumination spot on the target can be directly controlled, and the diameter of the lens can be directly constrained by setting the initial point coordinates. In this method, the edge-ray principle is used to simplify the extended light source model. The size and intensity distribution of the light spot irradiated by the light source to the target position were simulated by establishing a ray tracing model. The whole process was calculated using MATLAB software. The corresponding lens model can be obtained by fitting discrete coordinate points using Solid Works. Finally, the optical design software ZEMAX is used for simulation test. After shaping the laser light source with a luminous diameter of 1 mm, a circular and uniform spot is obtained at 100 m. For the point light source model, the divergence angle of 0.28° is achieved. Furthermore, an annular spot is also realized by setting the laser irradiation range, which provide a new solution for customized laser lighting.

Molecular dynamics simulations and machine-learning assisted study of the reaction path bifurcation: Application to the intramolecular Diels–Alder cycloaddition between cyclobutadiene and butadiene

The intramolecular Diels–Alder cycloaddition between cyclobutadiene and butadiene, which involves post-transition-state bifurcation (PTSB), has been investigated using the ring-polymer molecular dynamics (RPMD), classical MD and quasi-classical trajectory (QCT) simulations, and supervised machine-learning (ML) technique. The branching fraction of this reaction strongly depends on the simulation temperature. While QCT, classical MD and RPMD simulations performed at room temperature, starting from the ambimodal transition state (TS), showed the similar dynamics, QCT overestimated the minor branching fraction at low temperature. The supervised machine-learning analysis revealed that the initial coordinates and momenta for low frequency modes at the ambimodal TS contribute to the branching dynamics. The classical MD and RPMD methods follow similar conditions to quantum Boltzmann distributions, whereas the artificially localized phase distribution, considering that the zero-point energy is wedged into the classical particles. As a result, the QCT method can provide inadequate bifurcation dynamics, such as the overestimation of the minor product.

In silico induced effect of N-ε-lysine acetylation on microtubule stability and subsequent interaction of microtubule-associated proteins.

Plant systems have been considered valuable models for addressing fundamental questions of microtubule (MT) organization due to their considerable practical utility. Protein acetylation is a very common protein modification, and therate of acetylation can be modulated in cells in different biological states, and these changes can be detected at a molecular level. Here, we focused on K40, K112, and K394 residues as putative acetylation sites, which were shown to exist in both plants and mammals. Such residual effect of acetylation causes critical but unclear effect on MT stability. In turn, it was shown that acetylation indirectly affects the probability of interaction with different MAPs (Microtubule-associated proteins). In a multiscale study using an all-atom force field to reproduce several lattice-forming elements found on the surface the microtubule, we assembled a fragment of a plant microtubule composed of nine tubulins and used it as a model object along with the existing human complex. Triplets of tubulins assembled in a lattice cell were then simulated for both human and plant protein complexes, using a coarse-grained force field. We then analyzed the trajectories and identified some critical deformations of the MAP interaction surface. The initial coordinates were used to investigate the structural scenario in which autophagy-related protein 8 (ATG8) was able to interact with the MT fragment.

Computing aberration coefficients for plane-symmetric reflective systems: a Lie algebraic approach.

We apply the Lie algebraic method to reflecting optical systems with plane-symmetric freeform mirrors. Using analytical ray-tracing equations, we construct an optical map. The expansion of this map gives us the aberration coefficients in terms of initial ray coordinates. The Lie algebraic method is applied to treat aberrations up to arbitrary order. The presented method provides a systematic and rigorous approach to the derivation, treatment, and composition of aberrations in plane-symmetric systems. We give the results for second- and third-order aberrations and apply them to three single-mirror examples.

Optimization Method of Square Hole Measurement Based on Generalized Point Photogrammetry

The theory of generalized point photogrammetry extends the traditional point-based photogrammetry to line-based photogrammetry, expanding the application scope of photogrammetry in engineering. In order to solve the problem of accurate positioning between the square rod and the square hole in the current project, the position of the square hole should be accurately measured first. For this purpose, an optimization method of square hole measurement based on generalized point photogrammetry is proposed. This method first uses the traditional photogrammetric method to calculate the initial coordinates of the four points of the square hole and extract the four line segments on the image. The error equation based on generalized photogrammetry is constructed by the constraint conditions between the four spatial points, and the iterative calculation is carried out until the error is less than the threshold or the iteration number is reached. The reliability of the method is verified by numerical simulation experiments and engineering experiments. The experimental results show that the method can effectively improve the measurement accuracy and can rapidly converge. The method has high engineering application value.

Control System of the Aircraft’s Propulsion Device at Take-off with the Derated Thrust

The nonlinear control system of the aircraft propulsion system at take-off with the derated thrust at a running start stage on the runway (R) is considered. The mathematical model of rise of an object taking into account the different perturbing influences, such as starting mass, status of a surface of the runway, wind perturbation, real value of the engine’s thrust is analyzed. The settlement trajectory of running start based on of a priori the set model parameters of an object and the environment is defined. For the solution of a task of thrust control, at a deviation of model parameters of an object and the environment from rated values, the nonlinear control law draft is under construction. In work, the scheme of synthesis of a thrust control system, which is implemented based on a method of linearization of nonlinear model by feedback on an output, is offered. This method comes down to creation of nonlinear differentiable conversion of initial coordinates. With use of an assumptions the robust nonlinear control law providing forming a controlt signal with engine’s thrust for deviation compensation between rated and real running start trajectories in the absence of complete a priori information about take-off parameters was constructed. Conditions of respect for technical stability of running start of the aircraft, taking into account restrictions on the maximum value of draft of the propulsion system and the maximum length of running start on the runway were investigated. And the criterion of the emergency termination of take-off of the aircraft, when resources of the propulsion system do not allow to compensate the having mismatch between settlement and real trajectories of running start is offered. The received criterion allows to form a signal for take-off stopping and passing to the mode of the emergency termination of running start on the runway.